1. Field of the Invention
This application is directed to an improved process of making propane sulfonates which are useful as surfactants having high tolerance for brine and excellent thermal and hydrolytic stability.
2. Description of the Prior Art
Propane sulfonates of various polyethoxylated alcohols are known surfactants. Propane sulfonates are also known to have high tolerance for brine coupled with thermal and hydrolytic stability. However, propane sulfonates of alcohols and thiols have only been prepared in the literature by reaction of alkali metal salts of the alcohols or thiols with propane sulfone. This is a convenient high yield laboratory synthesis but is not desirable on a large scale for several reasons. Foremost among them are the fact that (1) such a reaction requires multistep synthesis and purification of propane sultone (2) propane sultone is expensive to purify and its overall yield of 80-90% limits the yield in the preparation of propane sulfonates and (3) propane sultone is a known carcinogen. Therefore processes involving the use of propane sultone must utilize expensive controls to minimize worker exposure but despite such controls its use will always engender some risk.
The preparation of allyl ethers or sulfides is also well known in the literature, however, the use of the procedure described herein to convert alcohols or thiols to propane sulfonates in a single reactor as far as is known to applicant is novel and unobvious. There is, however, one report in the literature of a two step attempt at a similar process for the preparation of propane sulfonates of tertiary amines [J. Amer. Oil Chem. Soc., 53, 60 (1976)] but it reports the process produces excessive quantities of undesirable "iso-sulfonate" whose presence degrades the performance of the product. This of course is most undesirable.